Well, more features in web apps isn't what I want; it is instead more and better features in the browser itself, such as:
- User stylesheets and user scripts.
- Ability to save and recall form data using local files.
- Ability to load animated GIF/PNG as videos.
- Request/response overriding (this can also be used to add the Do Not Track header).
- ARIA view (even for display on screen, not only for visually impaired).
- Better keyboard commands.
- Table of contents view (displaying the list of <h1>, <h2>, etc).
- Developer console (which I think newest versions of Chrome and Firefox already have, anyways).